Low vitamin D can mean trouble

Both a vitamin and a hormone, vitamin D comes primarily from exposure to the sun’s rays, food or supplements. It is essential in keeping our muscles and immune system strong, and also helps form and strengthen bones by allowing the body to absorb calcium. Without adequate vitamin D, bones become thin and brittle, which may lead to an increased risk of falls and fractures in older individuals.

What causes low levels of vitamin D?“Certain factors may limit your ability to obtain vitamin D through sunshine absorption, including seasonal conditions, living in northern latitudes, time of day, time spent indoors during daylight hours, use of sunblock and clothing coverage,” says Gay Bonilla, RD, CNSC, an advanced practitioner and dietitian at Sharp Grossmont Hospital.

Bonilla notes that individuals with lighter skin are able to absorb vitamin D more easily and quickly through sun exposure compared to darker-skinned individuals. In addition, vitamin D from food or supplements may be difficult to absorb due to conditions such as Crohn's disease, celiac disease, inflammatory bowel disease, fat malabsorption disorders, pancreatic insufficiency, cystic fibrosis, cholestatic liver disease or bariatric surgery. Use of anticonvulsant or antiretroviral medications can also reduce levels of vitamin D. Inactive and obese individuals tend to have lower vitamin D levels.

Ensuring you get enoughThe National Institutes of Health (NIH) currently recommends that healthy people get the following amounts of vitamin D each day:

Children and adults ages 70 and younger: 600 international units (IU)

Adults ages 71 and older: 800 IU

Pregnant and lactating women: 600 IU

“But the NIH recommendations may not be enough to achieve desired vitamin D levels,” Bonilla says. “Some researchers suggest following the Endocrine Society recommendations of at least 600 IU a day for ages 9 to 18. However, in order to consistently achieve goal levels, 1,000 IU a day may be required. For those who are 19 years and older, including pregnant and lactating women, at least 1,500 to 2,000 IU a day may be required to maintain adequate vitamin D levels.”

Bonilla recommends the following tips to ensure you are getting your daily requirement of vitamin D:

Eat foods that contain a natural source of vitamin D, such as eggs, mackerel, salmon and canned tuna, as well as fortified foods, such as cereal, dairy, almond and soy products.

Have your blood level of vitamin D checked by your doctor.

Take a vitamin D3 (cholecalciferol) supplement to meet the daily goal if your dietary vitamin D and sun exposure is limited. Discuss the amount that’s right for you with your doctor.

While sunblock is vital for protection against skin cancer, sunburn and sun damage, you should allow a few minutes of sunblock-free sunshine daily (10 minutes for those with light skin or 20 minutes for those with dark skin).

This story was updated in February 2019 to reflect the most recent medical research on this topic.